Air filter



FIG. 1 is a front perspective view of an air filter showing our new design;

FIG. 2 is a front view thereof;

FIG. 3 is a cross sectional view taken through line 3-3 in FIG. 1;

FIG. 4 is a left side view thereof;

FIG. 5 is a right side view thereof;

FIG. 6 is a top view thereof;

FIG. 7 is a bottom view thereof; and,

FIG. 8 is a rear view thereof.

The broken-lines in the drawings show portions of the filter that form no part of the claimed design. 

CLAIM The ornamental design for an air filter, as shown and described. 